watch Brian Bromberg's videos, awesome thumb-down player
Brian Bromberg - it's like a "
whole other musician" - a superbly-prolific, multi-genre and melodiously-attractive composer, arranger, producer, bass player (DB & BG), etc...
His dedication to the bass instrument makes it easier for Brian Bromberg to use "
almost any technique" while playing the bass. His deep and excellent knowledge of various melodic/harmonic/rhythmic/composition devices makes it easier (for Brian) to overcome any technical "impurities"/challenges/obstacles/etc... on the bass. Brian's profound sense of Musicianship (based on a long and very successful musical career) allows him to "hide" any technical "exceptions" that could easily "torpedo" any other musician.
Brian Bromberg's drumming experience has set a solid foundation about Groove, "ghost notes", rhythmic subdivisions, etc...
(Remember the drummer, Mark King?)
About Brian's "thumb down" slapping technique.
As a "thumb up" slapper, I don't feel comfortable (I feel "insecure"/in less control if I try to slap with my thumb down. Also, that thumb down technique precludes me from using the Double Thumb technique - one of my favorite things while slapping, but...
At the same time, that thumb down slapping position allows a bass player to easily(!) switch between the regular fingerstyle picking and Slapping.
In addition, the "thumb down" wrist movement axis provides extra flexibility for the horizontal (more or less the same string/s) "speedy" execution of rapid/fast, "muted/ghost" notes, while the "thumb up" wrist movement axis supports the vertical (between different strings) rapid/fast note "action.